2005 ford mustang rough idle

[quote=”stwarrior23″ post=158821]So im new to this forum, but have been to plenty of mustang forums with this problem. so i have a 2005 ford mustang v6 automatic transmission with 95k on it in florida, united states of america.

So it has this sort of rough idle or what i think is a rough idle, doesnt seem normal to me and only happens in drive or reverse when under load, in park or neutral its fine. it all started when my gauge cluster went out and had to get it replaced and the shop put the rpms around 500 and it idle at 650-700 before that so i complained and they wouldnt raise it because they said normal is 500-750 and i didnt think anything of it because well they where supposedly experts.

So now a couple months later i have sort of a rough idle and every mechanic i ask says its gonna cost you and we may or may not find the problem and it can be because of your mods(dont think so had them before and it was fine ) so ive taken my problems to google.

so far i have replaced the fuel filter, cleaned throttle body and maf sensor and they are both pristine clean, i reset my ecu with alligator clips because i took the throttle body off. I installed a new coil pack, new spark plug wires and plugs both because needed and thought it would help. i also sprayed some amsoil power foam into my engine and let it take all the carbon out but i didnt see much carbon or anything when i did it, didnt seem to do much.

so now im still no where, the resetting ecu helped for about a day and then went back to its normal ways. everthing seems to help but just for a few days or just a few hours of driving. so now im stumped and either thinking i need to raise the rpms or have a dealer look at it
Also if i slightly put my foot on the gas to anything above 500 it sounds and feels so much better. and when i go its fine no lag or anything it never loses power always does 0-60s fine never had any problem when going at any speed just at idle when stopped in drive, doesnt matter cold or hot
Any advice would be greatly appreciated and thank you for reading this.[/quote]

Other forums on this model of Mustang list the idle RPM as 700 minimum. I have, however, dealt with a transmission that when you shift it into drive or reverse it idles horrible. That was caused by a vacuum leak.

Computer controlled cars don’t have a set idle number, it adjusts with the load and conditions. If there are any modifications to the air intake system, I would re-install the factory parts to rule out any fault with the parts. It appears to be a drive by wire throttle body, so doing a manual reset of the idle speed may not have actually set a proper idle speed. But rather may have reset to known good default settings.

http://www.ericthecarguy.com/faq/solving-automotive-idle-problems

I assume no CEL? Can you scan it for fuel trim numbers?

Have you checked your engine mounts just to rule that out?

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